The present invention relates to heaters for heating process fluids used in the fabrication of integrated circuits on semiconductors. More particularly, the present invention relates to an in-line fluid heater including a parabolic lamp vessel and a parabolic reflection vessel for generating parallel heat energy rays to heat processing fluids.
The fabrication of various solid state devices requires the use of planar substrates, or semiconductor wafers, on which integrated circuits are fabricated. The final number, or yield, of functional integrated circuits on a wafer at the end of the IC fabrication process is of utmost importance to semiconductor manufacturers, and increasing the yield of circuits on the wafer is the main goal of semiconductor fabrication. After packaging, the circuits on the wafers are tested, wherein non-functional dies are marked using an inking process and the functional dies on the wafer are separated and sold. IC fabricators increase the yield of dies on a wafer by exploiting economies of scale. Over 1000 dies may be formed on a single wafer which measures from six to twelve inches in diameter.
Various processing steps are used to fabricate integrated circuits on a semiconductor wafer. These steps include deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal interconnection pattern, using standard lithographic or photolithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby etching the conducting layer in the form of the masked pattern on the substrate; removing or stripping the mask layer from the substrate typically using reactive plasma and chlorine gas, thereby exposing the top surface of the conductive interconnect layer; and cooling and drying the wafer substrate by applying water and nitrogen gas to the wafer substrate.
Many of the various processing steps, including etching and chemical vapor deposition (CVD), used in the semiconductor fabrication process require heated process fluids or chemicals for the formation of integrated circuits on the wafer substrate. In general applications, various types of heaters which are designed to prevent particle contamination of the process chemicals or fluids during heating are widely used in hydraulic systems. These heaters heat the fluids typically either by conduction from a coated heating element immersed in the fluids, or by radiation of heat energy from a heat source through an inert transparent tube to the fluids.
A common drawback of the conductor-type heaters is that the coating material on the heating element frequently becomes damaged, and this results in particle contamination of the fluids to be heated. Furthermore, the heater typically lacks both a warning system to notify personnel of the damaged coating on the element and a protective mechanism which would otherwise prevent further contamination of the fluids. Although radiation-type heaters are frequently equipped with differential pressure detectors or moisture sensors which monitor and alert personnel to the leakage of fluids through cracks that form in the quartz tube, the heaters are not equipped with any protective mechanism and thus, particles from the cracked tube still contaminate the fluid. Consequently, particle contamination of the chemical baths caused by the damaged heaters of each type reduces the wafer throughput and the yield of circuits on the wafer. Moreover, both the conductive-type and radiation-type heaters tend to be inefficient, and radiation-type heaters are attended by a potential fire risk.
Accordingly, an object of the present invention is to provide a new and improved heater for heating fluids in a variety of applications.
Another object of the present invention is to provide a new and improved heater for heating process fluids or chemicals used in the fabrication of semiconductor integrated circuits.
Still another object of the present invention is to provide a fluid heater which overcomes several of the drawbacks of conventional fluid heaters.
Yet another object of the present invention is to provide a fluid heater which may be equipped with a leak detector or detectors.
A still further object of the present invention is to provide a fluid heater which is efficient and utilizes a parabolic reflector to transmit parallel heat energy rays to a fluid to be heated.
Still another object of the present invention is to provide a radiation-type heater which may be equipped with at least one leak detector that is capable of notifying personnel of the presence of a fluid leakage in the heater.
Another object of the present invention is to provide a radiation-type heater which may be equipped with a leak detector or detectors operably connected to a heater controller and buzzer or alarm to facilitate shutdown of the heater and notification of personnel in the event of the leakage of fluid into the heater.
Yet another object of the present invention is to provide a radiation-type heater which is safe to operate and wherein potential fire risk is substantially reduced.
In accordance with these and other objects and advantages, the present invention comprises an in-line fluid heater including a heater housing that contains a parabolic lamp vessel which houses an infrared lamp. A parabolic reflection vessel in the heater housing is separated from the parabolic lamp vessel by a convex lens. A quartz plate seals the heater housing, and at least one, and typically, multiple leak detectors may be provided in the heater housing. The interior reflective surface of the reflection vessel reflects the heat energy in parallel rays through the quartz plate and to the fluid to be heated. The leak detectors may be connected to an RC circuit which operates a controller to actuate a buzzer or alarm and terminate operation of the heater upon leakage of fluid into the heater housing.